Process of converting photographic silver-prints into colored prints.



UNITED STATES PA w ARTHUR TRAUBE, orcnARLorrnNBURe, GER-MANY, 'nssrenon ro ACTIEN GESELL- soHAr'r FUR ANILIN FABRIKA'IION, or BERLIN, GERMANY.

PROCESS OF CONVERTING PHOTOGRAPHIC SILVER PRINTS INTO COLORED PRINTS. J

No Drawing.

T all whom it may concern:

' 13c 1t known that I, ARTHUR TRAUBE, doctor of plnlosophy, chemist, a SllbJBCt of the King of Prussia, German Emperor, residing at "16 ielandstrasse, Charlottenburg, kingdom of Prussia, German Empire, have invented new and useful Improvements in Processes of Converting Photographic Silver-Prints into Colored Prints, of WlllCll the following is a specification.

t It isknownthat in the optical sensitizing of halogen silver layers the desired effectonly occurs when the color employed directly colors the silver haloid. This phenomenon may be utilized for the conversion of silver prints into pure color prints by transforming the metallic silver prints into prints composed of silver compounds, coloring the prints of silver compounds so formed and eliminating the silver compounds from these prints, by means of fixing compounds To do this it is necessary to transform the metallic compounds of the picture into commay be obtained directly from silver prints.

In examining the question which silver compound was the best suited for the application of the color the surprising fact appeared that silver iodid, which hitherto could not be sensitized at all, presents so great an aflinityfforespecially basic colors, that in aqueous solutions of such colors it becomes colored with great intensity within a few minutes and retains the color in such a manner that no color is given oifhowever long washing With water may be carriedout. A large number of experiments carried out with many silver salt-s and silver double salts have failed to reveal-one which presents a greater aiiinity to colors than silver iodid.

The pictures composed of silver iodid and basic colors have the property that fixing compounds eliminate the silver iodid without attacking the basic colors. The treatment of the said colored print by means of fixing Specification of Letters Patent.

Application filed May 15, 1907. Serial No. 373,773.

Patented Apr. 14, 1914.

compounds dissolves therefore the silver iodid whereas the basic colorsremain. One obtains finally a picture free of silver-compounds and only composed of basic colors.

In accordance with what has been stated the conversion of a silver print into a colored print is efiected in the following manner:The silver print obtained. in the ordinary way on dia-positive emulsions of any a suitable origin, is transformed by known means into a print consisting of silver iodid or other compounds capable of being colored directly, whereupon the coloring is efle'cted A in suitable coloring baths. After a short time the deposit of the color on the silver compound will have taken place, whereupon the excess of color is removed from the gelatin film by a short soaking. The silver iodid prints thus obtained, which in respect of transparency even of the deepest shadows are especially suited for projection purposes, must be subjected to a fixing process for eliminating the silver compound from the picture when used for polychrome photography which requires completely transparent partial pictures.

Any of the known fixing processes maybe employed; for example, the fixing may be carried out by immersingthe print in a solution of sodium thiosulfate and washing the print. The concentration of the thiosulfate solution may be 1 part by weight thiosulfate in 100 parts by weight water.

Coloring materials of any kind may be used if the precipitation of the coloring material in the form of an insoluble lake or salt is effected by the addition of appropriate substances to the fixing solution for example, a solution of sodium thiosulfate.

This addition depends upon the nature of the coloring material. When the coloring is eflected by means of a basic coloring material, for instance quinolin red of a concentration 1:1000 tannin is added to the fix-- ing bath; when coloring with acid colorants,

for instance alizarin of a concentration leaves behind a color picture. I In any case it is merely a question of adding to the fixing bath (solvent for silver iodid or other silver compounds) those substances which with the coloring material give insoluble colored compounds.

What I claim as my invention, and desire to secure by Letters Patent, is

The process of converting silver prints into pure color pictures, which consists in converting the material of which the picture is composed into substances capable of being' colored directly and soluble in fixing compounds, then coloring the pictures with basic dyes and treating t 1e colored pictures DR. ARTHUR TRAUBE.

Witnesses:

HENRY HAsrER,

WOLDEMAR HAUPT, 

